Early diagnosis of prostate cancer often increases the likelihood of successful treatment or cure of such disease. Current diagnostic methods, however, depend largely on population-derived average values obtained from healthy individuals. Personalized diagnostic methods are needed that enable the diagnosis, especially the early diagnosis, of the presence of prostate cancer in individuals who are not known to have the cancer or who have recurrent prostate cancer.
Leukocytes begin as pluripotent hematopoietic stem cells in the bone marrow and develop along either the myeloid lineage (monocytes, macrophages, neutrophils, eosinophils, and basophils) or the lymphoid lineage (T and B lymphocytes and natural killer cells). The major function of the myeloid lineage cells (e.g., neutrophils and macrophages) is the phagocytosis of infectious organisms, live unwanted damaged cells, senescent and dead cells (apoptotic and necrotic), as well as the clearing of cellular debris. Phagocytes from healthy animals do not replicate and are diploid, i.e., have a DNA content of 2n. On average, each cell contains <10 ng DNA, <20 ng RNA, and <300 ng of protein. Non-phagocytic cells are also diploid and are not involved in the internalization of dead cells or infectious organisms and have a DNA index of one.
The lifetime of various white blood cell subpopulations varies from a few days (e.g., neutrophils) to several months (e.g., macrophages). Like other cell types, leukocytes age and eventually die. During their aging process, human blood- and tissue-derived phagocytes (e.g., neutrophils) exhibit all the classic markers of programmed cell death (i.e., apoptosis), including caspase activation, pyknotic nuclei, and chromatin fragmentation. These cells also display a number of “eat-me” flags (e.g., phosphatidylserine, sugars) on the extracellular surfaces of their plasma membranes. Consequently, dying and dead cells and subcellular fragments thereof are cleared from tissues and blood by other phagocytic cells.
The prostate specific antigen is currently one of the most widely used diagnostic measures used to detect prostate cancer. However, false negatives and false negatives are common, resulting in mistreatment of patients with no prostate cancer or overtreatment of patients with non-lethal prostate cancer. Thus, improved methods for detecting prostate cancer are needed.